How does the HUP battery handle such deep discharge?

There are many factors that determine the maximum amount of power that can safely be taken out of the battery for a given number of times. This is called the "Depth of Discharge" or DOD. The first is the chemical composition of the positive plate. For deep cycling, a precise amount of antimony is added to the grid structure while it is being created. Then the active material (also called "paste") that actually does the work is applied to the grid structure. The thickness of the the active material (paste) is the second most necessary requirement for deep cycle batteries. Deep cycle batteries have fewer, but thicker plates than shallow cycle batteries. An example of shallow cycle batteries are car batteries that have many thin plates made with a calcium additive in the frame.